Process and apparatus for removing condensates from gas



9, 1941. H. J. STOEVER PROCESS AND APPARATUS FOR REMOVING CONDENSATES FROM GAS Filed Oct. 18, 1938 2 Sheets-Sheet 1 Ewe Tzy" Aug. 19, 1941; v H V' R 2,252,738

PRObESS AND APPARATUS FOR REMOVING CONDENSATES FROM GAS Patented Aug. 19, 1941 PROCESS AND APPARATUS FOR REMOVING CONDENSATES FROM GAS Herman J. Stoever, Ames, Iowa, assignor to The United Gas Improvement Company, a corporation of Pennsylvania Application October 18, 1938, Serial No. 235,692

Claims.

This invention pertains generally to the liqueflcation and removal of readily condensible materials from a gaseous mixture, and pertains particularly to the recovery by liqueflcation of valuable substances from manufactured gas.

Manufactured gas such as carburetted water gas, oil gas, coal gas, etc., contains considerable quantities of valuable hydrocarbons which may be recovered upon a reduction in temperature of the gas. In the recovery of such materials on a large scale, however, considerable difiiculty is experienced with the solidification of certain components of the gas such as water, benzene, etc., in the heat exchange equipment, such solidification resulting in inefflcient heat exchange and/or stopp ges due to the building up of ice layers on the surfaces of heat exchange equipment.

A feature of this invention is the avoidance of heat exchange difliculties due to solidification of gas components. 3

Another feature of the invention is the employment as a cooling liquid of an absorbing oil which comprises condensate produced in the process. 7

Another feature of the invention is the provision of a process and means for the continuous removal from a gas of readily condensible materials-without the necessity of shutting down to thaw out solidified materials, or of duplicating the equipment.

A further feature of the invention resides in the utilization of the cold gas after'leaving the last stage of its cooling to condense a part of the refrigerant and thereby reduce the load on the cold gas in a manner to avoid stoppages.

whichwould be occasioned if this gas were used to cool the incoming warm gas in a gas tov gas heat exchanger.

Further features of the invention reside in the construction, arrangement and combinations of parts, and in the steps, sequences of steps and combinations of steps of the process, all of which together with other features will become more apparent to persons skilled in the art as the specification proceeds and upon reference to the drawings in which:

Figure 1 diagrammatically illustrates one ernbodiment of the invention;

Figure 2 is a sectional elevation (shown broken) illustrating the lower portion of a spray tower of Figure 1; and

Figure 3 is a diagrammatic illustration of another form of the invention.

Referring now more particularly to Figure 1 at H), H and I2 are shown vertically arranged spray towers which are preferably free from any type of phase contacting material such as packing, bubble plates, etc. i

Each'of the towers 18, H and I2 is provided at its top with a spray head l3, I4, and I5 respectively, and at its bottom with a liquid-solid separator l5, l1, and I8 respectively. I

Spray heads l3, l4, and 15 are identical in every respect. The same applies to liquid-solid separators l6, I1, and I8, the liquid-solid separator l6 being illustrated in detail in Figure 2.

Liquid-solid separator 16 has a liquid off-take l9 leading to a pump 28, the outlet of which is connected to the inlet 2| of a fluid space illustrated diagrammatically at 22 of heat exchanger 23. Outlet 24 of fluid space 22 is connected to spray head l3.

Likewise, liquid-solid separator H has a liquid off-take 26 leading to pump 21 the outlet of which connected to the inlet 28 of a fluid space ill trated diagrammatically at 23 of heat exchanger 30. Outlet 3| of fluidspace 28 is connected to spray head ll.

Also liquid-solid separator l 8 has aliquid oil'- take 33,1eading toa pump 34 the outlet of which is connected to the inlet 35 of a fluid space illustrated diagrammatically at 33 of heat exchanger 31. Outlet 38 of fluid space 36 is connected to spray head l5.

Liquid oil-takes i9, 28, and 33 also lead to drain valves 40, 41, and 42 respectively.

The other fluid space 4|, #5 and, of heat exchangers 23, 30 and 31 respectively is essentially an evaporating space for a liquefied refrigerant such as ammonia.

Fluid space 44 of heat exchanger 23 is connected adjacent its top through line 48 to the inlet of third stage compressor 49. The outlet of compressor 89 is connected through line 50 to fluid space 5| of condenser 52, the other fluid space 5301 which being provided with a suitable cooling liquid such as water.

The outlet of fluid space M is connected by line to the inlet of fluid space 56 of heat exchanger 51. The other fluid space 58 of heat exchanger 51 will be referred to hereinafter.

, The outlet of fluid space 58 is connected by line 60 to fluid space 44 through expansion valve 6|.

Fluid space 45 of heat exchanger 39 is connected by line 83 to the inlet of second stage be referred to hereinafter.

A liquid outlet from fluid space 66 is connected by line I8 to line II, the latter connecting fluid space 44 with fluid space 45 through expansion valve I2.

A vapor outlet from fluid space 66 is connected by line 69 to line 48.

Fluid space 46 of heat exchanger 3'! is connected by line I4 to the inlet of first stage compresser I5, the outlet of which is connected byline IE to the inlet of fluid space 11 of condenser I8.

The other fluid space I9 of condenser I8 will be referred to hereinafter.

Fluid space 11 has a vapor outlet 89 leading to line 63, and a liquid outlet 8| leading to line 82,

' the latter connecting fluid space 45 with fluid jacent the bottom of tower II through line 81!.

Tower H adjacent its top is provided with a gas outlet which is connected to a gas inlet adjacent the bottom of tower I2 through line 98.

Tower I2 adjacent its top is provided with a gas outlet which is connected to the inlet of fluid space I9 of condenser I8 through line 89.

The outlet of fluid space 19 is connected to the inlet of fluid space 68 of condenser 61 through line 99.

The outlet of fluid space 68 is connected to the inlet of fluid space 58 of heat exchanger 51 through line -9I The outlet of fluid space 58 is connected to line 92 which leads to any suitable point such as a gas holder not shown.

A broken sectional elevation of the lower portion of tower I9 is shown in Figure 2 and comprises a casing 94 having an inlet 95 leading from the main portion of tower I8, intermediate arcuate portions 98 and 91 conforming to the periphery of a rotating strainer 98, and wells 99 and I for the accumulation of liquid and solid respectively.

Off-take I9 is connected to well 99 and 01T- take I0l controlled by valve I92 is connected to well I89.

Well I00 is provided with a heating coil I99.

In the operation of the apparatus shown in Figures 1 and 2, gas to be treated enters the system through line 86 and passes up through tower II) where it-is met by a downward spray of cooled absorbent liquid comprising material previously condensed from the gas in this tower.

The up flowing gas is cooled by the down flowing liquid causing the more readily condensible materials to condense therefrom, and drop to the bottom of tower III along with the spray.

In addition, considerable quantities of the more soluble portions of the gas are carried down in solution in the down flowing liquid. This liquid collects in the bottom of tower I0, and flows down through'inlet 95 of liquid-solid separator I6, impinging upon the rotating strainer 98 thereof. The liquid passes down through the strainer and collects in well 99, and any solid material such as water ice, or benzol ice is retamed by the radial screens I94 of strainer 98 and is deposited in well 1198.

The solid material collecting in well I09 is melted by heat supplied by any convenient means such as through heating coil H93, and the liquid thus produced is withdrawn through ofi-take MI by opening valve I92.

The liquid collecting in well 99 is withdrawn continuously through off-take I9, a part being recirculated through pump 28, fluid space 22 and spray head I3, and the rest flowing through valve 49 to a suitable storage tank not shown.

Gas leaving the top of tower I9 enters the bottom of tower I l through line 81.

The treatment of the gas in tower II is in all respects similar to the treatment in tower II! with the exception that the temperature is considerably lower. The operation of tower I I and its accessories is in all respects similar to that of tower I 9 and its accessories.

The gas leaving the top of tower II enters the bottom of tower I2 through line 88.

The treatment of the gas in tower I2 is in all respects similar to the treatment in towers I I3 and II with the exception that the temperature in tower I2 is considerably lower. The operation of tower i2 and its accessories is in all respects similar to that of tower in or II and their respective accessories.

The cold gas leaving the top of tower I2 passes serially through heat exchangers I8, 61, and 51, and finally passes through line 92 to storage.

The absorbing liquid supplied to tower I9 is cooled in fluid space 22 of heat exchanger 23, the fluid space 22 being submerged in a liquefied re- -frigerant containedin fluid space 44, the cold being produced by the evaporation of the refrigerant in fluid space 44.

Referigerant vapor flows from fluid space 44 through line 48 to the inlet of compressor 49, the compressed vapor flowing through line 59 into fluid space 5| of heat exchanger 52 wherein the vapor is condensed upon being cooled by a cooling medium such as water flowing through fluid space 53.

Liquefied refrigerant flows from fluid space 5| through line 55 into fluid space 56' of heat exchanger 51 wherein it is further cooled by cold gas flowing through fluid space 58.

Liquid refrigerant flows from fluid space 56 by line 69 into fluid space 44 through expansion valve BI, the evaporation in fluid space 44 being, of course, produced by the reduction in pressure on the liquid refrigerant.

Liquid refrigerant from fluid space 44 flows by line 1| through expansion valve 12 into fluid space 45.

Because of the reduction in pressure on the liquid refrigerant as it passes into fluid space 45 which is accompanied by further evaporation, the temperature in fluid space 45 is considerably lower than the temperature in fluid space 44. i As a result the temperature of the absorbing liquid leaving fluid space 29 is considerably lower than the temperature of the absorbing liquid leaving fluid space 22, and the temperature of the spray at I4 is considerably lower than the temperature of the spray at I3.

Vapor produced in fluid space 45 flows through line 63 to the inlet of compresser 64 and the compressed vapor flows through line 65 into fluid space 66 of condenser 61, wherein it is at least partially liquefied due to cooling as a result of the flow of cold gas through fluid space 68.

Liquefied refrigerant produced in fluid space 66 flows through line I into line 'II and is returned through expansion valve I2 to fluid space 45 along with liquid refrigerant flowing from fluid space 44.

Cooled vapor from fluid space 66 flows through line 69 to line 48 and joins the vapor flowing from fluid space 44 to the inlet of 'compresser 48;

Liquid refrigerant from fluid space 45 flows by line 82 through expansion valve 83 into fluid space 46 of heat exchanger 31, the temperature in fluid space 46 being considerably lower than the temperature in fluid space 45 because of the reduction in pressure on and consequent evaporation of the liquid refrigerant as it passes through 7 expansion valve 83.

flows through line 8| to line 82 where it joins the.

liquid refrigerant flowing through line 82 to fluid space 46.

Cooled refrigerant vapor flows from fluid spac 11 through line 80 to line 63 where it joins refrigerant vapor flowing from fluid space 45 'to compresser 64.

It will be seen that by a variation of tempera tures and pressures in the refrigeration system, the temperatures of the sprays in towers I0, II and I2 may be varied over a wide range.

As an example of the temperatures which may obtain throughout the composite system, the gas to be treated may enter tower I0 at 90 F., and be met by a spray at 35 F., the temperature in fluid space 44 being 32 F,

The gas leaves tower I0 and enters tower II at 37 F. The spray of absorbing liquid enters.

tower II at -3'I F., the temperature in fluid space 45 being 40 F.

The gas leaves tower II and enters tower I2 at 35 F. The spray of absorbent liquid 'enters tower I2 at --'Z F.. the temperature in fluid space 46 being -60 F.

The gas leaves tower I2 and enters fluid space The gas enters fluid space 68 at 42 F. and leaves at 28 F.

The gas enters fluid space 58 at 28 F. and

leaves at 70 F., or in other words at substantially atmospheric temperature depending, of course, upon the season of the year. It will be noted that substantially all of the refrigeration available in the gas under treatment is recovered before the gas leaves the system, and that while a certain amount of refrigeration is lost through the condensate leaving towers I8, II, an d I2. the latter might be readily recovered and utilized by means of efiicient heat exchangers. 1

Since the towers I0, II, and I2 contain no packing or other contacting medium, no stoppage occurs as a result of the solidification of gas components, that is, as a result of what is commonly known as frost. Consequently, it is unnecessary to have 'a duplication of equipment to permit on and off stream operation for thawing purposes.

The process is a continuous one which permits considerably closer regulation and control over the composition of the condensates produced.

Should the solid material tend to adhere to the radial screens of the rotating strainers of liquidsolid separators I6, I1, and I8, it is merely necessary to by-pass a portion of the incoming gas in a manner to cause it to flow into the respective tower through the radial screens.

Suitable by-passes are illustrated at I06, I01 and I08, these by-passes being controlled by valves I09, H0, and III respectively.

The point of entry of by-pass I06 is illustrated in Figure 2.

It will be noted that gas entering the casing 94 through by-pass I06 enters between the radial screens I04. Such gas will pass upwardly through the radial screens I04, thereby raising the temperature thereof. The. quantity of gas thus by-passed is, of course, sufficient to remove any solid matter adhering to the radial screens.

The by-passed gas, of course, passes up into the tower and continues on through the system along with the gas admitted to the tow-er in the regular way.

Another form of the invention is illustrated in Figure 3 wherein tower H5 is provided with a spray II6 supplied with absorbing liquid taken from the bottom of the tower through off-take Hi. This absorbing liquid passes through pump H8, is cooled in refrigerating plant H9, and passes through a liquid-solid separator I20 before its delivery to the spray head I I6.

The construction of tower II5 may be in all respects similar to the construction of towers III, II, and I2, including th liquid-solid separators at the bottoms thereof.

The incoming gas enters through line I22, heat exchanger I23, and line I24 into the bottom of tower H5.

The incoming gas while flowing through fluid space I25 of heat exchanger I23, is brought into heat exchange relationship with the treated or outflowing gas. The treated gas leaves tower H5 at the top thereof and flows through line I26 to and through fluid space I21 of heat exchanger I28 and then through line I28 to storage.

It will be seen that the temperatures at various points may be varied as desired over a considerably wide range. Therefore, the following is merely illustrative.

The incoming gas enters through line I22 at 20 C. and is brought into heat exchanger relationship with the cold treated gas in heat exchanger I23, whereby its temperature is reduced to 0 C. The gas enters tower II5 through line I24 at this temperature and ascends therethrough while being brought into contact with a. downwardly moving spray of absorbing liquid which enters the tower H5 through spray head H6 at '70 C.

As a result, the temperature of the gas is reduced to 60 C. before it flows out through line I26 into heat exchanger I23. The temperature of the gas is brought back to 15 C. in heat exchanger I23 and it then flows through line I 28 is passed through liquid-solid separator 520 before its delivery to spray head H6. I

It should be noted that if desired, a liquid-solid separator similar to I20, might be inserted to Figure 1 between fluid space 22 and spray head l3, between fluid space 29 and spray head It, and/or between fluid space 36 and spray head l5.

Many other variations are possible.

For instance, any desired number of spray towers might be connected in series with corresponding refrigerating equipment.

Also one or more towersmight be eliminated.

For instance, tower I! might be cut out of the system by connecting line 88 directly to line 90 and shutting off flow through lilies 8E and 82.

Likewise, towers ll and i2 might be eliminated by connecting line 8'! directly to line 95 and shutting oif flow in lines 69 and H.

Furthermore, while the invention has been described in connection with the condensing or valuable hydrocarbons from manufactured gas, it is to be understood that, broadly speaking, it may be employed for the condensing of hydrocarbons from any other gas, such as natural gas, or in fact, for the treatment of gases generally.

Therefore, while I have particularly described my invention it is to be understood that this is by way of illustration and that changes, omissions, additions, substitutions and/or modifications might be made within the scope of the claims without departing from the spirit of the invention.

I claim:

1. A process for removing condensible materials from a gas comprising passing said gas serially through a plurality of unobstructed phase contacting paths countercurrently to absorbing liquid in spray form, the absorbing liquid entering each subsequent phase contacting path in the series being of a temperature lower than that of the absorbing liquid entering the preceding phase contacting path and sufficiently low to solidify a part of the condensate produced, the absorbing liquid introduced into each phase contacting path being a part of the condensate formed in said path after the separation of solid matter therefrom, and utilizing the cold stored up in the finally treated gas in the reduction of the temperature of the absorbing liquid entering said phase contacting paths.

2. Apparatus of the kind described, comprising a plurality of towers, each tower having an unobstructed phase contacting path, means for connecting said'towers for the passage of gas serially therethrough and countercurrently in each path to'a spray of absorbing liquid, means for obtaining the absorbing liquid for each path from the condensate formed in said path after separation of solidified material, means for reducing the temperature of the absorbing liquid for each path prior to its re-entry into said path,

I said last mentioned means maintaining the respective absorbing liquids entering said paths at successively lower temperatures in the series, and

-means for segregating and removing solidified material produced in each phase contacting path.

3. Apparatus of the kind described comprising a plurality of towers, each tower having an unobstructed phase contacting path, means for connecting said towers for the passage of gas serially therethrough and countercurrently in each path to a spray of absorbing'liquid, means for obtaining the absorbing liquid for each path from the condensate formed in said 'path after ducing the temperature of the absorbing liquid for each path prior to its re-entry into said path.

material produced in each phase contacting path, and means for utilizing the cold in the finally treated gas in reducing the temperatures of said absorbing liquids.

4. Apparatus of the kind described comprising a plurality of towers, each tower having a phase contacting path adapted to permit the fall there through of solidified material, means for connecting said towers for the passage of gas serially therethrough and countercurrently in each path to a spray of absorbing liquid, means for obtaining the absorbing liquid for each path from the condensate formed in said path after the separation of solidified material, means for reducing the temperature of the absorbent liquid for each path prior to its re-entry into said path,

said last mentioned means maintaining the respective absorbing liquids entering said paths at successively lower temperatures in the series, means for segregating and removing solidified material produced in each phase contacting path, and means for successively utilizing the cold in the finally treated gas in reducing the temperatures of said absorbing liquids in the order of increasingly higher temperatures thereof.

5. Apparatus of the kind described, comprising a plurality of towers, each tower having an unobstructed phase contacting path, means for connecting said towers for the passage of gas serially therethrough and countercurrently in each path to a spray of absorbing liquid, means for obtaining the absorbing liquid for each path from the condensate formed in said path after separation of solidified material, means for reducing the temperature of the absorbent liquid for each path prior to its re-entry into said path,

said last mentioned means maintaining the respective absorbing liquids entering said paths at successively lower temperatures in the series and sufiiciently low in at leastone of said paths to solidify components of said gas, means forsegregating and removing solidified material produced in each phase contacting path, andmeans for successively utilizing the cold in the finally treated gas in reducing the temperatures of said absorbing liquids in the order of increasingly higher temperatures thereof.

6. A process for recovering valuable hydrocarbons by absorption from 'a manufactured gas containing a part which readily solidifies upon reduction in temperature, said part including benzene; which comprises countercurrently contacting said gas while flowing upwardly with a dispersed downwardly flowing absorbing liquid having a temperature suficiently low to solidify a part of the material which separates from the gas due to said contact, said contact taking place mit the downward fall through said phase conseparation .of solidified material, means for retacting path of solidified material, separating solidified material from the liquid mixture of absorbing liquid and absorbed material resulting from said contact of gas and absorbing liquid, and recycling a cooled part of said separated liquid mixture as absorbing liquid.

7. A process for recovering valuable hydrocarbons by absorption from a manufactured as containing a part which readily solidifies upon reduction in temperature, said part including benzene, which comprises flowing said gas serially through a plurality of phase contacting paths in each of which said gas is countercurrently contacted while flowing upwardly with a down- .wardly flowing dispersed absorbing liquid of considerably lower temperature, said contact taking place in a manner to permit the downward fall through any phase contacting path of solidified material formed in that path, the absorbing liquid in each subsequent phase contact-' ing path in the direction of gas flow being of a temperature lower than that oi the absorbing liquid in the preceding phase contacting path, the temperature of the absorbing liquid in at least one of said phase contacting paths being suificiently low to solidify a part of the material separated from the gas by absorbing liquid, separating any solidified material from the liquid mixture of absorbing liquid and absorbed material formed in each phase contacting path as a result of said contact, and recycling a cooled part of said separated liquid mixture of each phase contacting path as absorbing liquid in said particular phase contacting path.

8. A process for recovering valuable hydrocarbons by absorption from a manufactured gas containing a part which readily solidifies upon reduction in temperature, said part including benzene, which comprises flowing said gas serially through a plurality of phase contacting paths in each of which said gas is countercurrently contacted while fiowing upwardly with a downwardly flowing dispersed absorbing liquid of considerably lower temperature, said contact taking place in a manner to permit the downward fall through any phase contacting path of solidified material formed in that path, the absorbing liquid in each subsequent phase contacting path in the direction of gas flow being of a temperature lower than that of the absorbing liquid in the preceding phase contacting path, the temperature of the absorbing liquid in at least one of said phase contacting paths being sufficiently lowto solidify a part of the material separated from the gas by absorbing liquid, separating any solidified material from the liquid mixture of absorbing liquid and absorbed material formed in each phase contacting path as a result of said contact, recycling a cooled part of said separated liquid mixture of each phase contacting path as absorbing liquid in said particular phase contacting path, and utilizing the cold stored up in the finally treated gas in obtaining the low temperatures of the absorbing liquids of said phase contacting paths.

9. Apparatus of the kind described, comprising a tower having a phase contacting path adapted to permit the fall therethrough of solidified material, means for fiowing a gas upwardly and a dispersed absorbing liquid downwardly through said phase contacting path for countercurrent contact therein, means for reducing the temperature of said absorbing liquid sufliciently to solidify constituents of said gas, means for separating solidified material from the liquid mixture of absorbing liquid and absorbed material resulting from said contact of gas and absorbing liquid, means for passing relatively warm incoming gas through said separating means in heat exchange relationship with separated solidified material, and means for recycling a part of said separated liquid mixture obtained from said path as absorbing liquid in said path.

10. A process for recovering valuable hydrocarbons by absorption from a gas containing a plurality of hydrocarbons including benzene which readily solidifies upon reduction in temperature, comprising contacting said gas with an I 

